The present invention relates generally to bearing structures and, more particularly, to a bearing structure adapted for oscillatory motion when under heavy load conditions.
The present invention is an improvement over the compound bearings described and claimed in U.S. Pat. No. 4,331,367 to Trudeau et al. In that patent a sealed compound bearing consists of outer and inner members movable relative to each other, between which are disposed load carrying annular members comprising elastomeric rings held between the outer and inner members under compression, and a metallic ring insert disposed between and separating the two elastomeric rings.
It has been found that bearings, according to the prior art, although satisfactory and long-lived under average medium duty service, tend to deteriorate rapidly when subjected to extremely heavy loads, especially if subjected to heat simultaneously with heavy loads, and, more particularly, in assemblies where adverse conditions of heavy load and heat are accompanied by substantial vibrations and shocks and an exaggerated amount of twisting, or relative motion, between the inner member and the outer member of the bearing. Such extremely adverse conditions are particularly prevalent when spherical bearings are utilized as a junction between suspension members and frame members, such as shock absorber attachment means in heavy duty motor vehicles, for example military combat vehicles, which are generally poorly maintained and called upon to operate under extremely adverse conditions. It has been discovered that under such extremely adverse conditions, when the bearings are continuously subjected to rapid twisting cycles under extremely heavy loads with repeated high frequency shocks, prior art bearings tend to heat up and, when further subjected to heat from the ambient, they deteriorate rapidly. The lubricant impregnating the fabric annular members becomes very fluid and extrudes from the fabric, and the extreme heat chars the fabric annular members and destroys the nylon or other plasatic insert ring. It has also been discovered that because the prior art bearings are pre-loaded during manufacturing, they are relatively tight when new, and thus they provide a relatively stiff connection between the joined components and tend to generate heat when the engaged surfaces of the various components of the bearings are displaced relative to each other, due to the relatively high co-efficient of friction between the bearing element surfaces.
Further, in some prior art bearings, an elastomeric material, such as rubber, is used and, under stressful conditions, the rubber loosens from the bond between the shell and the rubber. This condition, of course, is not acceptable.